ENDOR study of vanadyl(2+) ion (VO2+) adsorbed on Y zeolite

Abstract

Ovtr the past two decades electron paramagnetic resonance (EPR) has been used extensively in studies of the structure of transition metal ion exchanged zeclues. Use is made of the fact that data on g values and metal ion byperfine splitting constants pro ... -lde an insight into the structure o( the cation binding site. In this contribution it will be shown thi'lt electron nuclear double resonance (ENOOR) makes it possible to measure t.he interactions between the unpaired electrons and auctear spins in the vicinity of the paramagnetic catlcn. Generally. these Interactions remain unresolved in the EPR spectra of these amorphous 1),"eD'lS. The experimental results demonstrate that the ENDOR technique can be usl!'d to stud.y cation solvation in the zeolite caYitlt$ and changes in cation eavircnmenr induoed b)' removal of Solvent molecule, or co-adsorbed molecules. It is shown tbtlt subtle uruetural changes that do not register in the EPR spectrum can have a profound dfect on the ENDOR spectra. The results presented here suggest Ihat ENDOR can be of great value in studies of transition metal ion adsorption on zeolites as well as other porous surfaces.